Ophthalmosaurus("eye lizard") is a genus of ichthyosaur from the Middle to Late Jurassic of Europe, North America, and South America. It had a graceful, 16-20-foot (5-6-meter) long dolphin-like body, but had a tail like a shark's. It had an almost toothless snout which it used to snap up fish and squid.

Ophthalmosaurus had eye sockets that were about the size of coconuts, which makes it have some the largest eyes in the animal kingdom. It also means it could have hunted in deep, dark waters as well as shallow waters around coral reefs and islands.

Ophthalmosaurus shared its watery Jurassic habitat with several species of ammonites and jellyfish. The first crocodiles (some of which are sea-going) and turtles appear in the Jurassic. Fish, corals, horseshoe crabs, and sharks also shared these warm, shallow seas. Liopleurodon ("smooth-sided teeth") was the top predator of the ocean ecosystem at this time and preyed upon Ophthalmosaurus. Giant Leedsichthys, a plankton-eating fish, would have provided shelter for Ophthalmosaurus. It also shared its home with several long-necked plesiosaurs including Cryptoclidus ("hidden clavicle") and Mureanosaurus ("moray eel lizard").